Production of pure sulphur



July 28, 1931; P. KOPPE Lsl'egfxj;

PRDUCTION 0F PURE SULPHUR Filed Aug. 8. 1929 2 Sheets-Sheet l 5mm/nba Paul Kawa@ @his SH01/muy #MHJNM- July 2s, 1931'1' p, KQPPE 1,816,084

PRODUCTION OF PURE SULPHUR Filed Aug. 8,-1929 2 sheets-Sheet 2 FSZ..

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. PAUL KOP-PE, ,0F NEUROESSEN, GERMANY, ASSIGNOR TO I.

' suphides are i sulphur l rrSicily;

A greenish Patented July 28, 1931 i viren STATES PATENT OFFICE G. FARBENINDUSTRIE AKTIENGESELLSCHAFT, 0F FRANKFOB/T-ON-THE-MAIN, GERMANY, A CORPORA- rorrori or GERMANY PRODUCTIGN OF URE SULPHUR Application led August 8, 1929, Serial No. 384,485, and in Germany September 22, 1928.

The present invention relates to the production of pure sulphur from polysulphide solutions.

'A process for the continuous production of sulphur from solutions of ammonium ypolysulphides has been described elsewhere, which these solutions are introduced into a liquid in a being maintained at atmospheric pressure and at a temperature above the melting point of sulphur.

closed vessel, the said liquid or velevated which lies A modification of thisr process is also known f which the solutions of polytreated with direct steam in a counter current in a separating column at a temperature which lies above the melting point of sulphur so that the sulphur separates out. The essential feature of the aforesaid and similar processes resides in the polysulphide solutions being decomposed at a temperature abovethe melting point of the sulphur, land invention relates more particularly to improvements in processes'involving this essential feature.

lThe sulphur fof a purity of Vfrom 99.98 to 99.99 per cent obtainable according to these processes is certainly very pure in comparison with the ordinary commercial broken which originates from 'America' or in thes'olid state, however,'it has a lor grayv green colouration which reduces its sellingvalue andis due to inorganic impurities, probably chiefly iron sulphide'and other dark coloured metal sulhides which pass over into the sulphur groin the solutions of polysulphides iirst obaccording to tained in the recovery of sulphur from fulfils all requirements as regards purity can be obtained in a simple manner by the processes hereinbefore referred to, by carry- ,ing out' the, separation of the sulphur from solutions of polysulphides in stages.

purpose ofindrectly chemicals and labour which 1.5 to 2 atmospheres in By the gradual decomposition of a solution of ammonium polysulphides which is apparently clear, but which contains impurities of the kind already described in colloidal solution, a perfectly pure sulphur can be attained at lirst and this sulphur satisfies all requirements as regards appearance, and purity by analysis. ln .consequence of the presence of ammonia and ammonium sulphide the impurities at first remain colloidally dissolved in the solution of polysulphides. The substances which give he sulphur the undesirable colouration separate out only towards the end of the decomposition of the ammonium polysulphides.

The nature of my invention will be further described with reference to the accompanying diagrammatic drawings which show the arrangements of apparatus in accordance with this'invention. In Figure l the decomposition of the solution of polysulphides is effected by indirect heating and in Figure 2 it is effected by direct-heating by means of steam in counter current, but the invention is not restricted to the arrangements shown in the drawings.

Figure l shows in section an arrangement of apparatus according to this invention in which D1 and D2 are two pressure tight vessels connected with eachother by a pipey Z, in which vessels coils of pipes which are to be heated by steam are arranged for the heating the liquid contents of the vessels. The solution of polysulphides to be decomposed is continuously' introduced under pressure at a in a quantity equal to that of the products formed by the decomposition of the solution of polysulphides, namely, ammonia, hydrogen sulphide and steam, which leave the vessels D1 and D2 through a pressure valve e which maintains a pressure for example of from the pressure tight vessels and run into a condenser K. The condensate, namely a solution of pure ammonium sulphide, runs oft' from the condenser K at f. The solution can then be employed again for the extraction of crude sulphur or materials containing free sulhur. p By alteration of the quantity of the inflowing solution of polysulphides and of the hot steam it is possible to regulate the temperatures in the pressure tight vessels, which may be read by means of thermometers 251, and t2, soV that a temperature prevails in D1 which is still above the melting point of sulphur but which is below the boiling point of pure water at the pressure prevailing in D1.Y For example, the quantity of the solution of polysulphides flowing in and the quantity of the hot steam may be regulatedV so that the temperature in D1 amounts to about 118o centigrade. Under these conditions the separation of the sulphur in the pressure tight vessel D1 continuously occurs in the presence of so much ammonium sulphide that the impurities remain in solution. The impurities, together with the undecomposed solution, are continuously led into D2 by means'of the pipe `Z, in which latter vessel the complete decomposition occurs at a higher temperature, for example at from about 125O to 127 centigrade. Very pure yellow sulphur continuously separa-tes out in D1, and is drawn loil continuously or periodically at b, whilst the sulphur which is drawn olii from D2 at c is less pure and is considerably coloured lby the impurities which it has'taken up.

Obviously a single pressure tight vessel lis suiicient instead of two, if the introduction of the solutionV the decomposition of out periodically and of polysulphides and the same are carried not continuously. In the ,lirst part of the decomposition from about to 90 per cent of the total sulphur obtainable can berecovered in a very pure state; after drawing oil' this quantity of sulphur the residual solution is worked up until it is completely decomposed. After drawing olf the remainingvquantityT of sulphur the whole of the aqueous residual liquid is removed from the pressure tight vessel, which may then be charged with a fresh quantity of a solution Vof polysulphides. By this'manner ofrworking, the great advantage of the continuous process and the uniform charging and especially of the condensation plant, is dispensed with, but the vprocess may be carried out in a simpler and cheaper apparatus.

Vldhen it is desired to recover large quantities ofA sulphur continuously Vwith the expenditure-of vthe least4 possible quantity of steam itis advantageousto employ the arrangement of apparatus in accordance with this invention shown in section in Figure 2.

separating column D, which contains fillers .of any kind having the greatest and smoothest possible surface, is divided into two chambers by an intermediate iloor a which is provided with a pipe 1 and a hood gree of purity of the of sulphur.

pour thus formed streams from the top of the column into a condenser through a pressure valve v. The mixture lolf still undecomposed solution of polysulphides and the sulphur which has already separated out, which is trickling through the upper chamber is trapped at a and iiows through a tube e into a reservoir B. The sulphur settles to the bottom of the reservoir B in the molten state, and may be drawn off at in a very pure form. The quantity of this sulphur amounts to 90 per cent or more of the quantity of sulphur, contained in the solution of polysulphides above the amount of sulphur bound in the form of ammonium sulphide.V It is equal in value to Sicilian roll sulphur in every respect.

The solution which is supernatantto the sulphur in the reservoir'k B again flows into the column D through a tube g, thisYV time into the lower chamber'thereof, and is there completely decomposed. rIhe water free from ammonium sulphide, together with the remainder of the sulphur, Hows into a reservoir C at the foot of the column D. From this reservoir C, the sulphur isremoved at c, and the water at h. This sulphur which contains the impurities, resembles commercial American broken sulphur, especially as regards its colour, Vbut the deformer, determined by analysis, is considerably higher than that ofthe latter.

What I claim is:

1. In the production of sulphur by Ydecomposition of a polysulphide solution at a temperature above the melting point of sulphur, the step of effecting the separation of sulphur in stages. i 7

'2. The process oi producing sulphur which comprises contacting a polysulphide,

solution with steam at a temperature above the meltingpoint of sulphur, thereby decomposing part ofthe polysulphide, separating the -sulphur formed, and again treating the remaining solution with steam at a temperature above the melting point 3. The process of producing sulpliur, which comprises contacting a polysulphide Y solution with steam at a temperature slightly above the melting point of sulphur, thereby decomposing part of the polysulphide, separating the sulphur formed, and again treating the remaining solution with steam at a higher temperature.

4. In the production of sulphur by decomposition of an ammonium polysulphide solution ata temperature above the melting point of sulphur, the step of eii'ecting the vseparation of sulphur in stages.

5. They process of producing sulphur, Which comprises contacting an ammonium polysulphide solution With steam at a temperature above the melting point of sulphur, thereby decomposing part of the polysulphide, separating the sulphur formed, and again treating the remaining solution With steam at a temperature above, the melting point of sulphur.

6. The process of producing sulphur, Which comprisesk contacting an ammonium polysulphide solution With steam at a temperature slightly above the melting point of sulphur, thereby decomposing part of the polysulphide, separating the sulphur formed, and again treating the remaining solution With steam at a higher temperature. Y

7. The processof producing sulphur from an ammonium Vpolysulphide solution containing inorganic impurities Which comprises carrying out the process in tvvo stages and effecting a partial decomposition in the rststage under a temperature slightly in excess of the melting point of sulphur so that an excess of sulphide is present to thereby retain said inorganicy impurities in solution, separating the sulphur formed in this stage and completely decomposing the solution in the second stage. f

i 8. The process of producing sulphur from an ammonium polysulphide solution which comprises passing the Vpolysulphide solution counter current to a stream of steam under pressure and a temperature slightly in excess of the melting point of sulphur to effect a partial decomposition of said solution to sulphur and sulphide, tapping oil said sulphur and treating the remaining solution With steam at a higher temperature.

1 In testimony' whereof I have hereunto set my hand.

c PAUL KOPPE. 

